Isomerization of hydrocarbons



Patented June 27, 1950 UNITED STATES ICE 2,513,103 7, a ISOMEIBIZATION or HYDROCARBONSZ Herbert J. Passino, Englewood, N. J assignor to The M. W. Kellogg Company, Jersey City, N. J

a corporation of Delaware No Drawing. Application August 8, 1945, Serial No. 609,715

This invention relates to the isomerization of hydrocarbons in the presenceof a catalyst mixture of hydrogen fluoride and boron trifluoride,

and is particularly applicable to the isomeriza- 13 Claims; (01. 260 6835) 2 process is a :hydrogen fluoride-boron trifluoride mixture. jlWhile these constituents need not be present in the form of a physical mixture, it is preferred that they be at' least. available forsimultaneous contact with the hydrocarbons undergoing theisomerization treatment, so that they function essentiallyias a single catalytic material. While the relative p'r'bportions of these constituents may vary within a considerable range, it is essential that the ratio of hydrogen 1 fluoride to hydrocarbon-reactants present in the time suiiicient to affect the degree of isomerization desired.

It has been found, however, that hydrogen fluoride-boron trifiuoride catalysts have, in com mon with other previously discovered catalysts,

a pronounced tendency to crack hydrocarbons as well as to rearrange them. This tendency to wards cracking activity seems to increase in ascending order along the carbon chain. ample, n-heptane and n-octane appear to be considerably more susceptible to cracking than does n-butane.

izing catalysts then do their. branched-chain isomers;

It is an object of this invention to provide an improved method for utilization of hydrogen For-ex- In like manner, the n-parafllns appear more susceptible to cracking from isomerreactionzone be relatively high. This constituent of the catalytic material should preferably be present in the reaction zone in an amount greater than 5% by weight of the hydrocarbon reactants present, and preferably in an amount equivalent to at least 10% by weight of the hydroc'arbon reactantspresent. The ratio of boron 'trifluoride to the hydrocarbon reactants in contact with the hydrogen fluoride-boron trifiuoride j'batalytic mixture also may vary within relatively wide-limits, but preferably the borontrifiuoride is present in amounts approximately equivalent to 0.5%-10% by weight of the hydrocarbon reactants.

In accordance with the present invention, the

, foregoing hydrocarbon conversion treatment is fluoride-boron trifiuoride catalysts in hydrocar bon conversion treatments whereby cracking. of the hydrocarbonsis reduced toa minimum.

A further object is to provide an improved process for catalytic isomerization of hydrocarbons in which suitable additives are used with hydrogen fluoride-boron trifluoride mixtures to efiectively inhibit cracking of the hydrocarbons undergoing treatment.

The hydrocarbons susceptible. of treatment in accordancewith this invention include the parafiins, and particularly those paraffin hydrocar bons having four or more carbon atoms per molecule.

or narrow-boiling fractions. Also, the narrowboiling, normally liquid fractions generally designated as refinery hexanes may be treated to increase the proportion of branched-chain hydrocarbons contained therein. In addition to the treatment of individual hydrocarbons or of containing constituents whichare subject tothe' desired reaction. These may include relatively narrow-boiling fractions, the process is applica ble to the treatment of mixtures of hydrocarbons wide-boiling fractions such as light or heavy naphtha and natural gasoline.

The catalytic material employed in the present Forexample. individual hydrocarbona. suchas n-bu-tane and n-heptane, maybe treated, to effect conversion to the corresponding isomers carried out in the presence of suitable cracking inhibitor, the presence of which in small amounts is sufiicient to appreciably decrease the amount of cracking. As a result, liquid product recovery is increased and the formation of butane and lighter fractions is decreased.

The conditions under which the hydrocarbon reactants and catalytic materials are contacted a in thereaction zone will depend somewhat upon thecracking of the hydrocarbons undergoing treatment, and the temperatures necessary to "effect the desired reaction. In the treatment of normally liquid hydrocarbons, it is usually desirable to maintain conditions within the reaction zone under which the catalytic materialsand the hydrocarbonreactants i are substantially .in the liquid phase. In certain-- applications, how-: ever, it is contemplated that both the catalytic materials and the hydrocarbon; reactants may. more suitably be maintained in the vapor phase.-, It is further contemplated that in the treatment.

of certain hydrocarbons both liquid-phase and vapor-phaseconditionsmay be desirable For.

example, it may ina proper case be found advan tageous to .pass afyapor mixture comprising the hydrocarbon reactantsland the boron trifiuoride 1 catalyst through a looidyof liquid hydrogen fiuo ride catalyst.

It liasbeeh found that small amounts of farofmatics, naphthen'e s, and 'isoparailins may sues cessfull'y 'be employed 7 as cracking inhibitors." Although the am'ountof additive may vary, dc

pending upon the particular feed-stock and-the 3 proportions of hydrogen fluoride-and borontrifluoride employed a's='a; catalyst, satisfactory results have been obtained when the amount of additive was in the range of about 0.5% to 1%.

In order to illustrate the invention, specific examples of procedure are indicated by the fol-* lowing tables: 1

Liquid Product, Wt. Per Ceut Iso-Pentane in Liquid Product, Wt.

' PerGent v 20 hydrogen fluoride-boron trifluoride m1xture as 17 by weight of benzene added. a, catalyst 0.3% by weight of benzene added.

Table II nun Number 1 2 a w 4 5 s 1 8 Additive1% by Wt Conditions:

Temperature, F 150 150 200 250 150 200 150 150 Pressure, p. s. 1. reaction." 275 110 210 375 110 205 110 110 Time,-Minutes 120 60 60 60 60 60 ,120 Cherge:

' n-Heptane,g1:ns 405 400 390 397 410 422 414 421 z HF 100 100 100 100 100 100 ,BF; gms 25 25 25 25 25 25 25 30 Yields .Liduid Product, Wt. Per

cent Per cent 04 and Lighter in .Liquid-Product- 32 2 1 7 Inspect 4 and 3 that by the presence of 1% by weight of benzene in the feed, theliquid product recovered was materially increased and the conversion of n-pentane to isopentane was doubled. In Runs Nos. 4 and 5, temperatures slightly higher than that of Run No. 3 were employed without any substantial loss of liquid product recovered.

Comparing Runs Nos. 2 and 5, in which the temperature and time conditions were substantially identical, it will be observed that the presence 'of 0.5% by weight of benzene in the feed stock resulted in a greatly increased recovery yield, in the order of 17% and77 respectively. The above-tabulated results show rather clearly that the addition of benzene as an inhibitor in amounts of 0.5% to 1% by weight greatly reduces cracking in the catalytic hydrocarbon conversion treatment of n-pentane employing a T Benzene.

. Methylcyclohexsne.

i i Isooctane.

' The initial runs, the conditions and results of which are indicated in Table I, were carried out on the use 'of inhibitors'in the catalytic'isomericonsequently a lower liquid recovery resulted,.

the comparative figures being 61%, as against 17% by weight. Runs Nos. 3, 4, and 5 were carried .out witha pentane feed to which had been added small amounts of benzene as a crackingv inhibitor. In Run No. 3, 1% by weight of benzene was added to the pentane feed-stock. Itwill be noted from a comparison of Runs NO 1 75 In Table II are summarized the results of a series of eight runs carried out on the isomeri I zation of n-heptane, both alone and in the presence of inhibitors. Run No. 1 was carried out using CP n-heptane as the charge or feed stock. From an observation of the figures denoting weight percent of liquid recovered, and the percent of C4s and lighter products in the liquid: recovered, as well asthe ASTM distillation data,

it is clear that extensive cracking has occurred. In Run No. 2, using approximately the same reaction conditions, but adding 1% by weight of benzene to the charge as an inhibitor, the liq? uid recovered was approximately double and the amount of butane and lower boiling fractions in the liquid products was decreased by about.30%. The ASTM distillation also showed a much nar- 1 rower boiling range product, which was a very,

good indication that the cracking reaction had 5 been appreciably inhibited. Runs Nos. 3 and 4 were carried out using the same inhibitor, name 1y benzene, at slightly higher temperatures, the other reaction conditions remaining substantially constant. In both of these runs the liquid recovery yields were much higher than was the case in Run No. 1, and butane formation was much less. In fact, Run No. 4, made at a tem'- perature 100 F. higher than that of Run No.1, showed a liquid recovery nearly double that of Run No. 1, and a reduction of butane in the liquid recovered to the extent of of that' of Run No. 1. In Runs Nos. 5 and 6,1% byweight of methylcyclohexane was used as the inhibitor,"

producing much the same results. In Runs No. 7 and 8 the temperatures were again lowered to 150 F. and 1% by weight of isooctane was used as an inhibitor. Here, again, the results were similar to those resulting from the use of benzene and methylcyclohexane as inhibitors, although it was noted that the liquid recovery yields were slightly higher and the production of butane was slightly increased.

Although I have described my invention'in connection with the embodiments illustrated by the results summarized in Tables I and II, it, is to be understood that it is not limitedto the particular embodiments set forth. While the ranges and values specified are typical, various modifications may be made without departing from the spirit of my invention. For example, the invention contemplates a satisfactory temperature range of l300 F. and a time range of 1-18() minutes in which to effect in its commercial application the desired degree of isomerization. In addition, the additives employed to inhibit cracking may be present in an amount of from 0.1 by weight of the hydrocarbon reactant or reactants.

From the foregoing examples, it is apparent that I have provided a novel and effective method for inhibiting cracking in the isomerization of hydrocarbons in the presence of a hydrogen fluoride-boron trifiuoride mixture. While I have illustrated my invention specifically in connection with the isomerization of n -butane and nheptane, it is, of course, obvious that it is equally applicable to the isomerization of other hydrocarbons having four or more carbon atoms in the molecule, or a mixture of the same, without departing from the spirit of the invention, and it is desired therefore that only such limitations shall be placed thereon as are specifically set forth in the appended claims.

I claim:

1, The method for isomerizing aliphatic paraffin hydrocarbons having at least four carbon atoms per molecule which comprises contacting said hydrocarbons simultaneously with hydrogen fluoride and boron trifluoride in the presence of an added low boiling isoparafiin as a cracking inhibitor, the hydrogen fluoride being present in an amount equivalent to at least 10% by weight of the hydrocarbon reactants and the boron trifiuoride being present in an amount equivalent to at least 0.5% by weight of the hydrocarbon reactants, and maintaining said contact for a time not exceeding about three hours and a temperature sufficient to effect the desired degree of isomerization.

2. The method for isomerizing aliphatic paraffin hydrocarbons having at least four carbon atoms per molecule which comprises contactin said hydrocarbons simultaneously with hydrogen fluoride and boron trifluoride in the presence of 6 an added low boiling. isoparaflin as a cracking inhibitor, the hydrogen fluoride. being present in an amount equivalent toat least 10 by weight of the. hydrocarbon reactants, the boron trifiuoride being present in v an amount equivalent to at least 0.5% by weight of the hydrocarbon reactants,

and the inhibitor being present in an amount fluoride in the presence of. an added low boiling iso'paraffln as a cracking inhibitor, the hydrogen fluoride being present in an amount equivalent to at least 10% by weight of the n-heptane reactant, the boron trifluoride being present in an amount equivalent toat least 0.5% by weight of the n-heptane reactant, and the inhibitor being present in' annamount equivalent to from 0.1%-5%by weight of the n-heptane'reactant,

and maintaining said contact at a temperature of I00300 F. for aperiod oi'from 1-180 minutes. 4:. The method for isomerizing n-pentane which comprises contacting said n-pentane simultaneously with hydrogen fluoride and boron trifluoride in the presence of an added low boiling isoparafiin as a cracking inhibitor, the hydrogen fluoride being present in an amount equivalent to at least 1.0% by weight of the n-pentane reactant, and the inhibitor being present in an amount equivalent to from 0.1 to 5% by weight of the n-pentane reactant, and maintaining said contact at a temperature of -300 F. for a period of from 1-180 minutes.

5. A process for converting normal heptane to an isoheptane with a minimum of conversion to other paraffin hydrocarbons, which comprises admixing with normal heptane a low-boiling isoparaffin hydrocarbon in an amount between about 0.5 and about 5 per cent by weight of the total hydrocarbons, subjecting the resulting admixture to reaction at a temperature between about 100 and about 300 F. in the presence of a liquid catalyst consisting of hydrofluoric acid and boron trifluoride, the boron trifiuoride being present in the catalyst in minor amount for a reaction time not exceeding about three hours to isomerize said normal heptane, and recovering from effluents of said reaction a hydrocarbon fraction containing an isoheptane so produced.

6. An improved process for isomerizing a parafiin hydrocarbon having at least four carbon atoms per molecule, which comprises admixing with said paraffin hydrocarbon a minor amount of a low boiling isoparafiin hydrocarbon, subjecting the resulting admixture to reaction under isomerization conditions in the presence of a liquid catalyst consisting of hydrofluoric acid and boron trifluoride, the boron trifluoride being present in the catalyst in a minor amount, main taining a contact time not exceeding about three hours and a temperature sufficient to effect the desired degree of isomerization, and recovering from efliuents of said reaction a hydrocarbon fraction containing an isomer of said paraflin hydrocarbon so produced.

'7. An improved process for isomerizing a parafiin hydrocarbon having at least four carbon atoms per molecule which comprises admixing with said parafiin hydrocarbon a minor amount of alow boiling isoparaffin, subjecting the resulting admixture to reaction under isomerization conditions in the presence of a catalyst consisting essentially of hydrofluoric acid and boron trifluoride, maintaining a contact time not ex-.

v 8. The process of claim 7 in which said par aflin-hydrocarbon is normal butane.

9. The process of claim 7 in which said paraffin hydrocarbon is normal pentane.

10. The processiof claim 7 in which said paraffin hydrocarbon is normal heptane.

. 11; The process for effecting the isomerization of a low boiling parafiin hydrocarbon while inhibiting. cracking conversion which comprises contacting such a hydrocarbon simultaneously with hydrogen fluoride and boron trifluoride in the presence of an added isoparafiin which is present in an amount sufiicient substantially to inhibit said cracking, maintaining a contact time not exceeding about three hours and a temperature sufficient to effect the desired degree of isomerization, and recovering from the effluent ofsaid isomerization a hydrocarbon fraction containing an isomeric paraflin so produced.

12. An improved process for isomerizing a paraifin hydrocarbon having at least four carbon atoms per molecule which comprises admixing with said paraffin hydrocarbon a minor amount of isooctane, subjecting the resulting admixture to reaction under isomerization conditions in the presence of a liquid catalyst consisting of hydrofiuoric acid and boron trlfluoride, the boron trifluoride being present in the catalyst in a minor amount, and recoveringfrom efliuents of said reaction a hydrocarbon fraction containing an isomer of said paraflin hydrocarbon so produced.

13. The process for effecting the isomerization of a low boiling parafiin hydrocarbon which comprises contacting such a hydrocarbon simultaneously with hydrogen fluoride and boron trifiuoride in the presence of a minor amount of added iso-octane, under conditions such that the desired degree of isomerization is efiected, and

recovering from the eflluent of said isomeriza tion a, hydrocarbon fraction containing an isomer of said paraffin.

i HERBERT J.-PASSINO.

:REFERENCES CITED The following references are of record in th file of this patent:

v 5 UNITED STATES PATENTS Number 

1. THE METHOD FOR ISOMERIZING ALIPHATIC PARAFFIN HYDROCARBONS HAVING AT LEAST FOUR CARBON ATOMS PER MOLECULE WHICH COMPRISES CONTACTING SAID HYDROCARBONS SIMULTANEOUSLY WITH HYDROGEN FLUORIDE AND BORON TRIFLUORIDE IN THE PRESENCE OF AN ADDED LOW BOILING ISOPARAFFIN AS A CRACKING INHIBITOR, THE HYDROGEN FLUORIDE BEING PRESENT IN AN AMOUNT EQUIVALENT TO AT LEAST 10% BY WEIGHT OF THE HYDROCARBON REACTANTS AND THE BORON TRIFLUORIDE BEING PRESENT IN AN AMOUNT EQUIVALENT TO AT LEAST 0.5% BY WEIGHT OF THE HYDROCARBON REACTANTS, AND MAINTAINING SAID CONTACT FOR A TIME NOT EXCEEDING ABOUT THREE HOURS AND A TEMPERATURE SUFFICIENT TO EFFECT THE DESIRED DEGREE OF ISOMERIZATION. 